Blender VSE 40 minutes for a 3 min proxy rebuild? Is there no way to make a proxy for only a single strip?
According to the documenation:1 &quot;Storage: Defines whether the proxies are for individual strips or the entire sequence. Per Strip: Proxies are stored in the directory of the input.&quot; So, the &quot;Per Strip&quot; option really does only specify where the proxy is located.
AFAIK, I think your problem is with the &quot;cut&quot;. You imported a 1-hour video and cut it to 20 min. This does not implicate that the strip is only 20 min. It only shows 20 min in the timeline. Dragging the handles will easily extend the strip until its original length.
So, you have to cut your video in a separate application like handbrake or ffmpeg and save the result as a new video. This is essentially what you did in your second attempt (adding a 20 min video).